CN114450130A

CN114450130A - Height correction system

Info

Publication number: CN114450130A
Application number: CN202080067199.3A
Authority: CN
Inventors: 池尻匡隆
Original assignee: Nidec Corp
Current assignee: Nidec Corp
Priority date: 2019-09-27
Filing date: 2020-09-23
Publication date: 2022-05-06
Also published as: JPWO2021060227A1; WO2021060227A1

Abstract

The height correction system has: 1, a workbench on the ground; 2 nd ground trolley; a multi-joint robot arm on the trolley having a front end effector; a storage device storing a correction table; and a controller. In the correction table, the heights of the end effectors from the upper surface to positions directly above the upper surface of the table are stored in association with the positions, and the reference heights of the end effectors from at least 3 reference positions defined in advance on the table upper surface to positions directly above the reference positions are stored. The controller causes the arm to operate with the reference operation parameter, measures the height from each reference position to the end effector, and corrects the height deviation by correcting the reference operation parameter based on the amount of deviation between the height measured for each reference position and the reference height stored in the correction table.

Description

Height correction system

Technical Field

The present disclosure relates to an altitude correction system.

Background

A robot system is known in which a component is transported using a multi-joint robot arm (hereinafter, simply referred to as "robot arm") disposed on a self-propelled carriage. A "tip end effector" such as a gripping portion that grips a component is provided at a tip end portion of the robot arm. When the carriage reaches the target work table, the robot arm grips the component by the tip end effector, and the component is moved to a specific position on the top plate of the work table by extending and contracting the robot arm, and is assembled to another component.

Japanese patent application laid-open No. 7-266268 discloses a hand positioning device capable of performing positioning including the height direction or inclination of a robot arm (hand). The hand is mounted on a mobile robot that travels on the ground. The hand positioning device photographs a mark (LED) provided on the surface of the table with a camera at the front end of the arm, and corrects the height position of the arm based on the image.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-266268

Disclosure of Invention

Problems to be solved by the invention

When assembling the conveyed component to another component, it is required to move the component to a position of the other component on the top plate of the table with a predetermined accuracy. The manufacturer of the robot system confirms the accuracy in a factory of the company before the robot system is shipped, for example. In this pre-shipment inspection, typically, a carriage and a work table are installed on a horizontal ground surface.

On the other hand, depending on the environment (e.g., factory of delivery destination) where the robot system is actually introduced, there may be a case where the floor on which the work table is provided and/or the floor on which the carriage travels are not perfectly horizontal. In such an environment, even when the robot arm is to be moved horizontally, the robot arm actually moves away from or approaches the top plate of the work table. For the robot arm, it is required to correct the position in the height direction and suppress the positional deviation within a predetermined accuracy.

Means for solving the problems

In an exemplary embodiment, the height correction system of the present disclosure has: 1, a workbench on the ground; 2 nd ground trolley; a multi-joint robot arm that is provided on the carriage and has a front end effector at a front end portion; a storage device which stores a correction table prepared in advance; and a controller that corrects a deviation in height from the upper surface of the work table to the front end effector due to the inclination of the 1 st floor surface and/or the inclination of the 2 nd floor surface using the correction table, and causes the articulated robot arm to operate on the workpiece on the upper surface of the work table, wherein the correction table stores a height of the front end effector from each of a plurality of positions in a region of at least a part of the upper surface of the work table to a position immediately above the position, the height of the front end effector corresponding to the position when the work table is set on a1 st reference floor surface and the carriage is set on a 2 nd reference floor surface and the articulated robot arm operates with a predetermined reference operation parameter, and the correction table stores a reference height of the front end effector from at least 3 reference positions defined in advance on the upper surface of the work table to a position immediately above the reference positions, the controller performs the following actions: detecting the at least 3 reference positions from the upper surface of the table; operating the articulated robot arm with the reference operation parameters, and measuring a height from each of the detected reference positions to the tip end effector; and correcting the reference operation parameter based on a deviation amount between the height measured for each of the reference positions and the reference height at each of the reference positions stored in the correction table, thereby correcting a deviation in height from the upper surface of the work table to the tip end effector, which is caused by the inclination of the 1 st floor surface and/or the inclination of the 2 nd floor surface, for each of the positions on the upper surface of the work table.

Effects of the invention

The accuracy of the height position of the arm during work can be improved even in an environment where the inclination of both the arm side and the work table side may vary.

Drawings

Fig. 1 is an external view of a robot system 1.

Fig. 2 is a hardware block diagram of the robot system 1, mainly the control device 200.

Fig. 3 is a diagram showing the robot system 1 provided in an environment for generating the correction table 230.

Fig. 4 is a diagram showing a specific example of the generated correction table 230.

Fig. 5 is a diagram showing an example of a table in which measurement results of the skew in the height direction of the robot arm a when the robot arm a is set on the horizontal plane are stored.

Fig. 6 is a diagram showing an example of a table in which measurement results of the inclination of the ground surface farf on which the vehicle 300 travels are stored.

Fig. 7 is a diagram showing an example of a table in which measurement results of the inclination of the ground surface FUref on which the work table U is installed are stored.

Fig. 8 is a diagram showing the robot system 1 introduced into a specific environment.

Fig. 9 is a perspective view of the robot system 1 set in a work environment.

Fig. 10 is a diagram showing the inclination of each position of the ground FA1 on which the dolly 300 travels.

Fig. 11 is a view showing the inclination of each position of the ground FU1 provided with the work table U.

Fig. 12 is a diagram showing 3 positions P1, P2, and P3 on the top plate Utop of the table U.

Fig. 13 is a diagram showing an example of the measurement results of the heights of the front end effector 100 at the 3 reference positions P1, P2, and P3.

Fig. 14 is a diagram showing an example of the difference result.

Fig. 15 is a diagram for explaining the plane approximation.

Fig. 16 is a diagram showing an example of the difference in height to the front end actuator at each position constituting a lattice point, which is obtained by plane approximation.

Fig. 17 is a flowchart showing a procedure of the process of the controller 210.

Fig. 18 is a diagram showing the robot system 2 that acquires characteristic data of the main work station MU.

Fig. 19 is a diagram showing an example of a table in which the skew measurement results of the main table MU are stored.

Fig. 20 is a diagram showing the robot system 3 in which the new arm NA and the main work table MU are combined.

Fig. 21 is a diagram showing an example of a table in which the measurement results of the skew of the new arm NA are stored.

Fig. 22 is a diagram showing the robot system 4 in which the main robot arm MA and the new work station NU are combined.

Fig. 23 is a diagram showing an example of a table in which the measurement results of the skew of the new work table NU are stored.

Fig. 24 is a diagram showing the biaxial automatic angle measuring table 400 and the microcomputer 500 provided on the work table U.

Fig. 25A is an external view of the biaxial automatic angle measuring table 400.

Fig. 25B is an external view of the biaxial automatic angle measuring table 400.

Fig. 26 is a flowchart showing a procedure of a process of the microcomputer 500 controlling the biaxial automatic angle measuring table 400.

Detailed Description

Hereinafter, an embodiment of the height correction system according to the present invention will be described with reference to the drawings. Hereinafter, a robot system will be described as an embodiment of the height correction system.

Fig. 1 is an external view of a robot system 1. The robot system 1 includes a multi-joint robot arm a (hereinafter, simply referred to as "robot arm a") having a distal end portion to which a distal end effector 100 is attached, a control device 200, a carriage 300, and a work table U.

The robot arm a has

joints

104 and 106 in addition to the waist portion 102, and the posture of the robot arm a is changed by rotating or extending and contracting the joints.

The distal end effector 100 is a device that is attached to the distal end portion of the robot arm a so as to enable the robot arm a to perform work. Typical examples of the front end effector include a grip portion, a nut rotator, a welding gun, and a spray gun. The front end effector can be replaced by a user as appropriate according to the use of the robot arm a.

The control device 200 controls the operation of the robot arm a. The waist portion 102 of the robot arm a is fixed to the upper portion of the control device 200. The control device 200 and the robot arm a are connected by a power supply cable and a control cable, not shown.

The carriage 300 is a device on which the robot arm a and the control device 200 are mounted and moved. In the present embodiment, the cart 300 is an automated guided vehicle that has wheels that generate a driving force (traction) for movement and that automatically travels. The automatic travel includes travel based on a command from an operation management system (not shown) connected to the automated guided vehicle via communication with a computer, and autonomous travel by a control device (not shown) provided in the automated guided vehicle. In the present embodiment, the control device 200 and the carriage 300 are connected by a control cable, not shown, and the carriage 300 can travel in response to a command from the control device 200.

The autonomous traveling includes not only traveling of the automated guided vehicle toward a destination along a predetermined route but also traveling following a tracking target. The automated guided vehicle may temporarily perform manual travel based on an instruction from an operator.

"automatic travel" may generally include both "guided" travel and "unguided" travel. The "guide type" is a system in which the inductor is continuously or intermittently provided and the guided vehicle is guided by the inductor. The "unguided type" refers to a type of guidance without providing an inducer. The carriage 300 according to the embodiment of the present disclosure has its own position estimating device, and can travel without guidance.

The "self-position estimating device" is a device that estimates a self-position on the environment map from sensor data acquired by an external sensor such as a laser range finder. The "external sensor" is a sensor that senses a state of the outside of the moving body. Examples of external sensors are laser range finders (also called range sensors), cameras (or image sensors), LIDAR (Light Detection and Ranging), millimeter-wave radar, and magnetic sensors.

The dolly 300 can simultaneously perform the self-position estimation and the environment Mapping by a so-called "SLAM (Simultaneous Localization and Mapping)" technique.

The table U has a top plate Utop. In the present specification, the top plate Utop may be referred to as "the upper surface of the table U". The robot arm a performs work on the top plate Utop. For example, the robot arm a assembles a workpiece (component) held by the front end effector 100 to a component placed on the top plate Utop. Alternatively, the robot arm a places the components held by the front end effector 100 at predetermined positions on the top plate Utop.

In the robot system 1, the carriage 300 travels on the ground FA, and the work table U is provided on the ground FU. In the present embodiment, the description is given of the case where the work table U is fixedly installed on the ground FU, but the work table U may be automatically driven with wheels that generate driving force for movement.

Fig. 2 is a hardware block diagram of the robot system 1, mainly the control device 200. The control device 200 has a controller 210 and a storage device 220. The controller 210 is a so-called computer, and includes, for example, a CPU (central processing unit), an internal memory (buffer, register), and communication terminals for transmitting and receiving data to and from the robot arm a and the cart 300, respectively.

The storage device 220 is, for example, a RAM. The storage device 220 holds a correction table 230. The calibration table 230 is a table in which positions and heights are associated with each other, which is measured in advance by operating the robot arm a in a predetermined environment. The details of the method of generating the correction table will be described later.

When the robot system 1 is shipped from a manufacturer and actually introduced into, for example, a factory at a delivery destination, the controller 210 of the control device 200 can correct the offset in the height direction of the robot arm a by the procedure described later, using the correction table 230 and the data acquired in the environment of introduction.

The description and explanation of the specific internal hardware configuration of the robot arm a and the cart 300 shown in fig. 2 are omitted. The robot arm a and the cart 300 may have hardware structures of a known robot arm and an automated guided vehicle (so-called AGV), respectively. With such a hardware configuration, the robot arm a and the cart 300 can operate in accordance with instructions from the controller 210 of the control device 200.

Next, a specific example of the correction table 230 and a process of generating the correction table 230 will be described with reference to fig. 3 to 7.

Fig. 3 shows the robot system 1 set in an environment for generating the correction table 230. Typically, the robot system 1 shown in fig. 3 is provided in an inspection factory of a manufacturer of the robot system 1. As another example, the robot system 1 may be temporarily installed in a delivery destination factory or the like and then moved to a different location in the factory.

In the environment for generating the correction table 230, the ground surface FUref on which the work table U is installed and the ground surface FAref on which the carriage 300 travels are known in advance. Therefore, the inclination of ground surface fref and the inclination of ground surface farf can be acquired in advance, and the correction table 230 can be generated using the acquired inclinations. In the present description, ground surface FUref on which table U is installed may be referred to as "1 st reference ground surface", and ground surface FAref on which truck 300 travels may be referred to as "2 nd reference ground surface".

As shown in fig. 3, the X axis and the Y axis correspond to the horizontal axis and the vertical axis of the correction table 230 described below.

Fig. 4 shows a specific example of the generated correction table 230. The right direction of the correction table 230 corresponds to the + X direction of fig. 3, and the lower direction corresponds to the + Y direction of fig. 3.

The meaning indicated by the correction table 230 shown in fig. 4 will be explained. First, a plurality of positions defined by X coordinates and Y coordinates are set to lattice points on the top plate Utop of the table U. The robot arm a was operated so that the tip end effector 100 was brought to a height of 150mm directly above each grid point, and the actual height at that time was measured. The "right above" is not limited to being perpendicular to the top plate Utop of the table U. This means that the grid points are located upward when viewed in the vertical direction.

The table in which the measured height is described in the coordinate position indicating the lattice point is the correction table 230. That is, the correction table 230 is a table in which the position on the top plate Utop when the robot arm a is actually operated in relation to the work table U is stored in association with the height of the end effector 100 at that time. For example, at the position of coordinates (-10 ), it should be a height of 150mm, but it means 149.6196mm in this robot system 1. In addition, the coordinate position and the value of 150mm are an example. The method of acquiring the coordinates and the height can be appropriately changed according to the size of the top plate Utop of the table U and the work position required for the end effector 100.

Various factors affecting the operation accuracy in the height direction of the robot system 1 are reflected in the correction table 230. Specifically, in the correction table 230, (1) a deviation in the accuracy of the robot arm a in the height direction, (2) the inclination of the floor surface FAref on which the cart 300 travels, and (3) the inclination of the floor surface FUref on which the work table U is installed are reflected. The variation in the accuracy in the height direction of the robot arm a may include a tilt when the waist portion 102 of the robot arm a is fixed to the control device 200, and a variation in the operation accuracy of each joint of the robot arm a.

The above-described main causes (1) to (3) are independently acquired in order to generate the correction table 230.

Fig. 5 shows an example of a table in which measurement results of the skew in the height direction of the robot arm a when the robot arm a is set on the horizontal plane are stored. The height of the front end effector 100 from the top plate Utop is measured in a state where both the ground on which the work table U is installed and the ground on which the carriage 300 travels are aligned with the horizontal plane. For the height measurement, for example, a method using a laser distance measuring device (not shown) attached near the tip end effector 100 is considered.

The controller 210 sequentially moves the front end effector 100 to a position 150mm above the coordinates (5 m, 5 n) (m: -an integer of 2 to 2, n: -an integer of 2 to 2), for example. Every time the position is changed, the laser distance measuring apparatus measures the height from the tip end effector 100 corresponding to each position to the top plate Utop when the robot arm a is operated so as to move from the top plate Utop to a height of 150 mm. In the height measurement result thus acquired, only the inclination in the height direction of the robot arm a is reflected without the influence of the inclination of the floor.

Fig. 6 shows an example of a table in which measurement results of the inclination of the ground surface farf on which the cart 300 travels are stored. Fig. 7 shows an example of a table storing measurement results of the inclination of the ground surface FUref on which the work table U is installed. These indicate the amount of deviation in the height direction from the horizontal plane at the position (X, Y). A positive value is given when the level is higher than the horizontal plane, and a negative value is given when the level is lower than the horizontal plane.

The value of the table (fig. 5) indicating the primary cause (1) at the position (X, Y) is represented as "V1 (X, Y)", the value of the table (fig. 6) indicating the primary cause (2) is represented as "V2 (X, Y)", and the value of the table (fig. 7) indicating the primary cause (3) is represented as "V3 (X, Y)". Then, the value V (X, Y) of the correction table 230 is calculated by the following equation.

(formula 1)

V(X，Y)＝V1(X，Y)+V2(X，Y)-V3(X，Y)

In the present embodiment, it is assumed that the top plate Utop of the table U is a flat surface with a negligible unevenness. However, when there are non-negligible irregularities on the top plate Utop and consideration is required for positioning the distal end effector 100 of the robot arm a, the value V (X, Y) of the correction table 230 may be generated by further considering a table obtained by measuring the irregularities at each position of the top plate Utop.

By the above consideration method and procedure, the correction table 230 can be prepared in advance. In this specification, the height of each coordinate constituting the correction table 230 is sometimes referred to as a "reference height" at that coordinate. In the present embodiment, at least 3 of the plurality of coordinates may be referred to as "reference positions". The coordinates of the reference positions are, for example (-10 ), (-10, 10) and (10, 10), and the positions of the ends of the top plate Utop are used. In the correction table 230, a height corresponding to the reference position is associated. The "reference height" and the "reference position" are explained later.

Next, a height correction method for operating the robot arm a in the height direction with high accuracy in an environment where the robot system 1 is actually introduced will be described.

In order to correct the height, predetermined data is acquired in advance.

Fig. 8 shows the robot system 1 introduced into a specific environment. Fig. 9 is a perspective view of the robot system 1 set in a work environment. The chain line shown in fig. 8 indicates the horizontal plane. In fig. 8 and 9, a ground FA1 on which the carriage 300 travels and a ground FU1 on which the work table U is provided are slightly emphasized and described so as to show an environment different from that of fig. 1. That is, the ground FA1 is different from the ground FA (fig. 1), and the ground FU1 is also different from the ground FU (fig. 1). The inclination of the ground FA1 or the ground FU1 may be different from the example of fig. 1. The same as the example of fig. 1, except for the inclination of the ground. Since the work table U and the robot arm a shown in fig. 1 are directly introduced into different environments, the robot system 1 in fig. 8 has the same variation in accuracy in the height direction of the robot arm a as the robot system 1 in fig. 1.

In the environment in which the robot system 1 is introduced, the inclination of the floor FA1 on which the carriage 300 travels and the inclination of the floor FU1 on which the work table U is provided can be measured. In the present embodiment, the installer separately obtains the inclination of the ground FA1 and the inclination of the ground FU1 and stores the data in the storage device 220 of the control device 200.

Fig. 10 shows the inclination of each position of the ground FA1 on which the carriage 300 travels, and fig. 11 shows the inclination of each position of the ground FU1 on which the work table U is provided. According to the example of fig. 10, the ground FA1 on which the carriage 300 travels is inclined to be higher toward the front (toward the + Y direction). On the other hand, according to the example of fig. 11, the ground FU1 on which the work table U is provided is inclined so as to be higher toward the right hand (toward the + X direction).

Next, the height of the robot arm a is measured under the introduced environment. When the correction table 230 is generated, the height is measured at each position of the lattice point (fig. 5). Here, however, it is only necessary to measure the height at least 3 positions. An example of automatic operation by the control device 200 will be described below.

Fig. 12 shows 3 positions P1, P2, and P3 on the top plate Utop of the table U. The 3 positions P1, P2, and P3 referred to herein are the same as the reference positions corresponding to the heights in the above-described correction table 230. Therefore, the reference positions P1, P2, and P3 are also referred to below. The reference positions P1, P2, and P3 have respective coordinates (-10 ), (-10, 10), and (10, 10).

The controller 210 of the control device 200 detects the above-described 3 reference positions from the top plate Utop. As an example of the detection method, the controller 210 may take an image of the top plate Utop by an imaging device (not shown) and determine 3 corners (end portions) of the top plate Utop recognized from the acquired image as the reference positions P1, P2, and P3.

The controller 210 operates the articulated robot arm, and measures the height from each detected reference position to the tip end effector. As an example of the measurement method, the controller 210 can use a laser distance measuring device (not shown) in the same manner as when the table shown in fig. 5 is generated.

Fig. 13 shows an example of the measurement results of the heights of the front end effector 100 at the 3 reference positions P1, P2, and P3.

The controller 210 corrects the deviation of the height according to the amount of deviation of the height measured for each reference position from the reference height at each reference position held in the correction table 230. The following description will be specifically made.

The controller 210 stores "reference operation parameters" in advance in order to operate the robot arm a. Consider an example in which the front end effector 100 is moved to a particular three-dimensional coordinate position. The controller 210 specifies the rotation direction and rotation angle of the motor of the waist portion 102 and the rotation direction and rotation angle of the motors provided in the plurality of joints, respectively, and transmits the specified values to the robot arm a as control amounts. The robot arm a rotates each motor by a predetermined angle in a predetermined rotational direction in accordance with the received control amount. The control amount for determining the posture of the robot arm a in order to move the tip end effector 100 to such a desired three-dimensional coordinate position is the "reference motion parameter". In the present embodiment, it is considered that the "reference operation parameters" are prepared in advance for positions 150mm above the grid points on the top plate Utop.

In the first place, if the operation is performed using the reference operation parameter, the front end effector 100 should be able to move to a desired three-dimensional coordinate position, but in a situation where the position in the height direction is displaced due to the above-described various factors, the "reference operation parameter" needs to be corrected so as to have the original height. By correcting the "reference operation parameter", it is possible to correct the deviation in height from the top board Utop to the front end effector 100 due to the inclination of the floor surface FA1 on which the carriage 300 travels and the inclination of the floor surface FU1 on which the work table U is provided, for each position of the top board Utop.

Therefore, the controller 210 calculates the difference between the measurement results obtained for the 3 reference positions P1, P2, and P3 and the value V in the correction table 230. Fig. 14 shows an example of the difference result. It can be known that although there is no error at the reference positions P1(-10 ) and P3(10, 10), an error of 0.4mm is generated at the reference position P2(-10, 10).

Since errors are obtained not only for the 3 reference positions but also for the respective positions constituting the lattice points, the present inventors performed plane approximation for the height deviation caused by the inclination of the ground surface FAref and the inclination of the ground surface futef.

Fig. 15 is a diagram for explaining the plane approximation.

By using the coordinate values of the reference positions P1 to P3 and the value V in the correction table, 3 points representing three-dimensional positions can be obtained. That is, 3 three-dimensional positions can be obtained by the set of values V of the correction table 230 at the reference position P1 and the reference position P1, the set of values V of the correction table 230 at the reference position P2 and the reference position P2, and the set of values V of the correction table 230 at the reference position P3 and the reference position P3. An imaginary plane developed with these 3 points is referred to as "plane Kref".

On the other hand, 3 points representing three-dimensional positions can be obtained using the coordinate values of the reference positions P1 to P3 and the acquired measurement results (fig. 13). That is, 3 three-dimensional positions can be obtained from the group of the reference position P1 and the height measured at the reference position P1, the group of the reference position P2 and the height measured at the reference position P2, and the group of the reference position P3 and the height measured at the reference position P3. An imaginary plane developed by these 3 three-dimensional positions is referred to as "plane Km".

According to the difference shown in fig. 14, the plane Kref and the plane Km share a point of coordinates (-10, -10, 149.6196) above the reference position P1 and a point of coordinates (10, 10, 149.948) above the reference position P3. That is, the plane Kref and the plane Km intersect with a straight line L passing through these 2 points. Further, it can be said that an error of 0.4mm occurs above the reference position P2.

The present inventors found the height corresponding to the positions of N grid points other than the reference position among the positions of the grid points set on the top plate Utop as the height to the plane Km in the environment in which the robot system 1 was introduced. That is, the controller 210 approximates the height at the position where the vertical lines respectively passing through the N positions constituting the lattice point intersect the virtual plane Km to the height to the front end actuator of each of the N positions.

Fig. 16 shows an example of the difference in height to the front end actuator at each position constituting a lattice point obtained by plane approximation. When the value V of the correction table 230 is added to the value of the difference table shown in fig. 16 for each position, the height of the robot arm a can be estimated under a newly introduced environment.

The controller 210 corrects the reference operation parameters of the 3 reference positions and the N positions so that the approximate heights at the respective positions approach the originally required height (150 mm in the present embodiment). Thus, the deviation in height from the top board Utop to the front end effector 100 due to the inclination of the floor surface FA1 on which the carriage 300 travels and the inclination of the floor surface FU1 on which the work table U is provided can be corrected for each position of the top board Utop.

In addition, it may be said that the accuracy of the height value at each position stored in the correction table 230 (fig. 4) is sufficiently high. In this case, the controller 210 may correct the reference operation parameters associated with each of the N positions so that the deviation amount (difference) between the height approximated to each of the N positions and the height stored in each of the N positions in the correction table 230 is smaller.

In step S10, the controller 210 detects each reference position from the top plate Utop (upper surface) of the table U.

In step S12, the controller 210 operates the robot arm with the reference operation parameters, and measures the height from each detected reference position to the tip end effector.

In step S14, the controller 210 corrects the reference operation parameter based on the amount of deviation between the height measured for each reference position and the reference height stored in the correction table for each reference position. This makes it possible to correct the deviation in height from the upper surface of the work table to the front end effector due to the inclination of the ground FA and/or the inclination of the ground FU for each position of the upper surface of the work table.

In the above description, it is not necessary that the controller 210 detect the 3 reference positions and measure the height, and other methods may be used. For example, if the accuracy of the movement in the horizontal direction can be sufficiently ensured, the controller 210 does not need to detect the 3 reference positions as long as the positions of the 3 reference positions can be taught in the horizontal direction and the robot arm a is stopped above the reference positions, respectively. Further, the position (height) of the tip end effector 100 above the 3 reference positions may be artificially measured, and the measurement result may be transmitted and stored in the storage device 220.

The example of the correction processing in the height direction in the case where the environment in which the correction table 230 is created assuming 1 set of the robot arm a and the work table U is different from the set environment has been described.

Hereinafter, 2 modifications of the correction process will be described.

As a modification 1, a description will be given of a correction process assuming that a specific robot arm and a work table are combined with the same robot arm and another work table are combined with the same work table and another robot arm is newly combined with the same work table.

As a modification 2, an example will be described in which a work table capable of adjusting the height and angle in the vertical direction is used without correcting the positional deviation in the height direction by the robot arm.

In modification 1, terms such as "main robot arm" and "main work table" are introduced. "main robot arm" and "main work table" refer to a specific robot arm and work table as a reference of combination. Hereinafter, reference numerals such as "MA" are given to the main robot arm, and reference numerals such as "MU" are given to the main work table. Examples of combinations of the main robot arm MA and the main work table MU are the robot arm a and the work table U in fig. 1 to 3. The hardware configurations of the main robot arm MA and the main work table MU are the same as those of the robot arm a and the work table U. Hereinafter, the same reference numerals are used as appropriate to describe the present invention.

In the present modification, an example will be described in which a different robot arm (new arm) different from the "main robot arm" and a different work table (new work table) different from the "main robot arm" are combined, and a different work table (new work table) different from the "main robot arm MA" and the "main work table MU" are combined.

First, characteristic data indicating characteristics unique to each of the main robot arm MA and the main work table MU is acquired.

The method of acquiring the characteristic data of the main robot arm MA is the same as the method of acquiring the table shown in fig. 5. That is, the skew in the height direction of the main robot arm a when the main robot arm a is set on the horizontal plane is characteristic data of the main robot arm MA.

On the other hand, the method of acquiring the property data of the work table MU is as follows.

Fig. 18 shows the robot system 2 that acquires the characteristic data of the main work station MU. Ground FU and FA are horizontal.

The controller 210 controls the main robot arm MA, for example, so that the front end effector 100 is located at a height of 150mm above the coordinates (-10 ) of the top plate Utop. Then, while maintaining this posture as it is, the controller 210 moves and stops the carriage 300 by a predetermined distance (for example, +5) in parallel to the X direction, and repeatedly executes the operation of moving and stopping the carriage 300. At each stop, the laser distance measuring device measures the height from the top plate Utop to the front end effector 100. As a result, the height measurement results at the coordinate positions of coordinates (-10 ), (-5, -10), (0, -10), (5, -10), and (10, -10) are obtained.

And further to a position shifted by +5 in the Y direction in the same manner, the measurement results of the height at each position of the coordinates (-10, -5), (-5, -5), …, (10, -5) of the top plate Utop are obtained. The same action is continued until a measurement of the height at the position of the coordinates (10, 10) is acquired.

The height measurement results obtained by the ground FU and FA being horizontal and maintaining the attitude of main robot arm MA can be said to reflect the "skew" of main table MU. Fig. 19 shows an example of a table in which the skew measurement result of the main work table MU is stored.

Next, an example of the height correction process in the case where the new arm NA and the main table MU are combined will be described.

Fig. 20 shows the robot system 3 in which the new arm NA and the main work table MU are combined. First, the control device 200 that controls the new arm NA acquires the measurement result of the skew of the new arm NA. The measurement method is the same as the measurement method using the skew in the height direction of the robot arm a described in association with fig. 5. When the skew of the new arm NA is measured, the new arm NA is set at the position of the main robot arm MA at the time when the skew of the main robot arm MA is measured. As described above, in the present modification, the robot arm a and the work table U in fig. 1 to 3 are given as an example of a combination of the main robot arm MA and the main work table MU. If this example is used, the new arm NA is set at the position of the robot arm a shown in fig. 3. The control device 200 and the carriage 300 on which the new arm NA is mounted need not be completely the same as the control device 200 and the carriage 300 on which the robot arm a is mounted in fig. 3.

Fig. 21 shows an example of a table in which the measurement results of the skew of the new arm NA are stored. The skew measurement condition is the same as that in the measurement of the skew of the main robot arm MA shown in fig. 5. Therefore, the measurement result shown in fig. 21 is characteristic data of the new arm NA. The value of the table at position (X, Y) is denoted as "V1_NA(X，Y)”。

As described above, the value V (X, Y) of the correction table 230 is calculated by (equation 1) described above. Again, (equation 1) is disclosed.

(formula 1)

V(X，Y)＝V1(X，Y)+V2(X，Y)-V3(X，Y)

"V1 (X, Y)" in this formula represents a main robot armSkew of MA. Therefore, "V1" is used instead of "V1 (X, Y)"_NA(X, Y) "the end of (1) of (type 2).

(formula 2)

Vrev(X，Y)＝V1_NA(X，Y)+V2(X，Y)-V3(X，Y)

The value Vrev (X, Y) of the correction table thus corrected can be obtained. V2(X, Y) and V3(X, Y) indicate values of a table storing results of measuring the inclination of the floor on which the truck 300 travels and values of a table storing results of measuring the inclination of the floor on which the main work table MU is installed, respectively. It needs to be measured according to the environment in which the new arm NA and the main work table MU are arranged.

The method of correcting the height of the front end effector 100 using the corrected correction table is as described above. That is, if the "robot arm a" described above is replaced with the "new arm NA", the height of the tip end effector 100 can be corrected even when the new arm NA or the main table MU is installed on a floor that is not a horizontal surface.

Next, an example of the height correction process in the case where the main robot arm MA and the new work table NU are combined will be described.

Fig. 22 shows the robot system 4 in which the main robot arm MA and the new work station NU are combined. First, the control device 200 acquires a measurement result of the skew of the new work table NU. The measurement method is the same as the measurement method of the skew in the height direction of the main table MU described in association with fig. 18 and 19. When the skew of the new work table NU is measured, the new work table NU is set at the position of the main work table MU when the skew of the main work table MU is measured. For example, the main work station MU is disposed at the position of the main work station MU shown in fig. 18.

Fig. 23 shows an example of a table in which the measurement results of the skew of the new work table NU are stored. The controller 210 calculates the difference between the table value and the table value storing the measurement result of the skew of the main table MU shown in fig. 19 for each position. The difference table in which the obtained differences are arranged for each position is the characteristic data of the new station NU based on the characteristic data of the main station MU. The value of the difference table at position (X, Y) is represented as "V_diff(X，Y)”。

The table shown in fig. 5 is characteristic data of the main robot arm MA when the main work table MU and the main robot arm MA are set in the horizontal plane. When a new work table NU is used instead of the main work table MU, the characteristic data of the new work table NU is reflected in the measurement result of the skew in the height direction of the main robot arm MA. In other words, by correcting the table shown in fig. 5 using the difference table, it is possible to obtain the characteristic data of the main robot arm MA when the new work table NU and the main robot arm MA are set on the horizontal plane.

Specifically, the value Vrev (X, Y) of the corrected correction table can be obtained by the following (expression 3).

(formula 3)

Vrev(X，Y)＝V1(X，Y)+V_diff(X，Y)+V2(X，Y)-V3(X，Y)

Further, V2(X, Y) and V3(X, Y) respectively indicate values in a table in which results of measuring the inclination of the floor surface on which the cart 300 travels are stored, and values in a table in which results of measuring the inclination of the floor surface on which the new work platform NU is installed are stored. It needs to be measured according to the environment in which the main robot arm MA and the new work station NU are set.

In the above description, by correcting the reference operation parameter of the robot arm, the variation in height from the upper surface (top plate) of the work table to the tip end effector is corrected. Hereinafter, the table having a mechanism (tilt adjusting mechanism) for adjusting the tilt of the top plate adjusts the tilt of the top plate, instead of correcting the reference operation parameter of the robot arm. In the present embodiment, a biaxial automatic angle measuring table is used as the tilt adjusting mechanism.

Fig. 24 shows a biaxial automatic angle measuring table 400 and a microcomputer 500 provided on a work table U. The microcomputer 500 controls the biaxial automatic angle measuring table 400 (hereinafter, simply referred to as "angle measuring table 400") to adjust the inclination of the top plate Utop of the table U.

First, the biaxial automatic angle measuring table 400 as a tilt adjusting mechanism will be described. In the case of using the biaxial automatic angle measuring table, the height of the tip end effector and the top plate can be adjusted so as to be constant without correcting the reference operation parameters of the robot arm. The absolute height in the Z-axis direction perpendicular to the top plate is adjusted by the motion of the robot arm.

In the present embodiment, a known biaxial automatic angle measuring table described in, for example, japanese patent application laid-open No. 2006-090510 is used. Hereinafter, a biaxial automatic angle measuring table described in fig. 2 and 3 of jp 2006-090510 a will be described.

Fig. 25A and 25B are external views of the biaxial automatic angle measuring table 400. Fig. 25A shows the goniometer stage 400 when the top plate of the slider 42 is in a state parallel to the ground. Fig. 25B shows the goniometer stage 400 tilting the top plate of the slider 42. The following describes an outline of the goniometer 400.

The goniometer 400 is configured by overlapping 2 stages each sliding on a longitudinal bending line in one axial direction, with the axes being perpendicular to each other, by rotating 90 degrees.

The slider 42 is provided to slide on a longitudinal bending line of the shaft body 41.

Specifically, the shaft body 41 is provided with the 1 st load section constituting member 47 in which the 1 st load groove 47a having a vertically curved shape is formed. On the other hand, the slider 42 is provided with a 2 nd load part constituting member 48 in which a 2 nd load groove 48a having a vertically curved shape is formed. The 1 st load groove 47a and the 2 nd load groove 48a face each other to form a load path 43, and a plurality of rolling elements (not shown) that roll in the load path 43 are arranged in the load path 43. These rolling elements are arranged so as to be held at predetermined intervals by a plate-like rolling element cage (not shown) that moves in the load path 43. Further, load paths 43 are provided at one location on the left and right sides of each of the stages after the stacking.

Each stage includes a servomotor 44 for driving the worm 46, a bearing 45 for receiving the worm 46, and a stopper screw 49 for preventing the rolling element supporter from coming off. The worm 46 is coupled to a drive shaft of the servomotor 44 via a coupling body. The worm 46 is screwed to a screwing portion (not shown) provided on the lower surface of the slider 42. When the worm 46 is driven by the servomotor 44, the screw portion is fed in a direction corresponding to the rotation direction of the worm 46, and the inclination of the slider 42 changes. When each servo motor 44 of both stages is rotated at a rotation speed corresponding to a desired movement amount, the inclination of the top plate of the slider 42 can be changed. The amount of movement can be known from the scale plate 50 indicating the amount of movement of the slider 42.

By fixing the top plate of the angle measuring table 400 and the back surface of the top plate Utop of the work table U, the inclination of the top plate Utop can be adjusted. The microcomputer 500 for controlling the angle measuring table 400 communicates with the controller 210, and the microcomputer receives data necessary for adjusting the inclination of the top plate Utop from the controller 210 to control the respective servo motors, or the microcomputer 500 may be omitted and the controller 210 of the control device 200 may directly control the respective servo motors of the angle measuring table 400. Specific examples of the former will be described.

Consider the situation shown in figure 15. The current top plate Utop is parallel to the imaginary plane Km. The microcomputer 500 acquires data of heights measured for the reference positions P1 to P3 corresponding to the Z coordinate of the position on the assumed plane Km from the controller 210. Then, the microcomputer 500 acquires data of the deviation amount of each reference height stored in the correction table 230. Then, the microcomputer 500 adjusts the inclination of the current top plate Utop (virtual plane Km) so that the height of the distal end effector 100 of the robot arm operated according to the current reference operation parameters is constant regardless of the position on the top plate Utop, based on the height and the amount of deviation measured for each of the reference positions P1 to P3. That is, by adjusting the inclination of the top plate Utop using the goniometer table 400, it is possible to correct the deviation in height from the top plate Utop to the front end effector 100 due to the inclination of the ground surface on which the work table U is provided and/or the inclination of the ground surface on which the carriage 300 travels, for each position of the top plate Utop.

In addition, the height of the front end effector 100 may not be strictly kept constant regardless of the position on the top plate Utop. For example, the microcomputer 500 may adjust the inclination of the top plate Utop so that the deviation amount between the height measured for each reference position and the reference height stored in the correction table at each reference position is equal to or less than a predetermined threshold value. The adjustment of the inclination of the top plate Utop in the present modification is a process that replaces the correction of the reference operation parameter of the robot arm. Other processes may be directly adopted in the present modification. Note that description of the processing in the case of actual combination is omitted for redundancy.

Fig. 26 is a flowchart showing a procedure of the process of the microcomputer 500.

In step S20, the microcomputer 500 receives the measurement results of the height from each reference position to the tip end effector when the robot arm is operated with the reference operation parameters from the controller 210. In the case where the microcomputer 500 does not have the correction table 230, the microcomputer 500 may also receive the correction table 230 from the controller 210.

In step S22, the microcomputer 500 adjusts the inclination of the upper surface of the work table based on the amount of deviation between the height measured for each reference position and the reference height stored in the correction table at each reference position. Thus, the microcomputer 500 corrects the deviation in height from the upper surface of the work table to the front end effector due to the inclination of the ground on which the carriage travels and/or the inclination of the ground on which the work table is provided, for each position of the upper surface of the work table.

In addition, the goniometer stage need not be biaxial, but may be triaxial. In the case of three axes, a vertical mechanism may be provided in the height direction (Z direction). For example, the linear stepping motor may be used to move up and down in the Z-axis direction. Since all of the three axes can be adjusted on the work table side, the height direction adjustment by the robot arm is not necessary. In other words, it is not necessary to include a process of adjusting the height direction in the operation program of the robot arm. When positioning in the three-axis direction on the robot arm side is ensured by a copying operation using another mechanical mechanism or a force sensor, the robot arm can be made to perform a certain operation by teaching playback, and fine adjustment can be performed on the work table.

Industrial applicability

The exemplary embodiment of the present invention can be used for a robot system having a robot arm requiring accuracy in the height direction.

Description of the reference symbols

A: a robot arm; FU, FA: a ground surface; u: an operation table; and (3) Utop: a top plate; 1: a robotic system; 100: a front end actuator; 200: a control device; 210: a controller; 220: a storage device; 230: a correction table; 300: a trolley; 400: a double-shaft automatic angle measuring table; 500: a microcomputer.

Claims

1. An altitude correction system, having:

1, a workbench on the ground;

2 nd ground trolley;

a multi-joint robot arm that is provided on the carriage and has a front end effector at a front end portion;

a storage device which stores a correction table prepared in advance; and

a controller that corrects a deviation in height from the upper surface of the work table to the front end effector due to the inclination of the 1 st floor surface and/or the inclination of the 2 nd floor surface using the correction table, and causes the articulated robot arm to operate on the workpiece on the upper surface of the work table,

wherein the content of the first and second substances,

in the calibration table, heights of the end effector from a plurality of positions in a region of at least a part of an upper surface of the work table to positions directly above the positions when the work table is set on a1 st reference floor surface and the carriage is set on a 2 nd reference floor surface and the articulated robot arm is operated with a predetermined reference operation parameter are stored in correspondence with the positions,

the calibration tables store reference heights of the front end effector from at least 3 reference positions defined in advance on the upper surface of the table to positions directly above the reference positions,

the controller performs the following actions:

detecting the at least 3 reference positions from the upper surface of the table;

operating the articulated robot arm with the reference operation parameters, and measuring a height from each of the detected reference positions to the tip end effector; and

by correcting the reference operation parameter based on the amount of deviation between the height measured for each reference position and the reference height at each reference position stored in the correction table, the deviation in height from the upper surface of the work table to the tip end effector due to the inclination of the 1 st floor surface and/or the inclination of the 2 nd floor surface is corrected for each position of the upper surface of the work table.

2. The altitude correction system of claim 1,

the controller corrects the reference operation parameter so that a deviation amount between the height measured for each of the reference positions and the reference height stored in the correction table at each of the reference positions is smaller.

3. The altitude correction system according to claim 1 or 2,

the at least 3 reference positions include a1 st reference position, a 2 nd reference position, and a 3 rd reference position of the upper surface of the work table,

storing the 1 st reference position in the correction table in correspondence with a1 st reference height to the front end effector at the 1 st reference position,

storing the 2 nd reference position in the correction table in correspondence with a 2 nd reference height to the front end effector at the 2 nd reference position,

storing the 3 rd reference position in the correction table in correspondence with a 3 rd reference height to the front end effector at the 3 rd reference position,

storing, in the correction table, other N positions on the upper surface of the table, where N is a positive integer, in correspondence with the respective heights of the N positions to the front end actuator,

the controller performs the following actions:

calculating an imaginary plane passing through 3 three-dimensional positions determined by the set of the 1 st reference position and the height measured at the 1 st reference position, the set of the 2 nd reference position and the height measured at the 2 nd reference position, and the set of the 3 rd reference position and the height measured at the 3 rd reference position;

approximating the heights at positions where the plumb lines respectively passing through the N positions intersect the imaginary plane to the respective heights of the N positions to the front end actuator; and

correcting the reference operation parameter for each of the N positions based on the amount of deviation between the height corresponding to each of the N positions in the correction table and the approximate height.

4. The height correction system of claim 3,

the controller corrects the reference operation parameter for each of the N positions so that a deviation amount between the height approximated for each of the N positions and the height for each of the N positions stored in the correction table is smaller.

5. The altitude correction system according to any one of claims 1 to 4,

the 1 st reference position, the 2 nd reference position, the 3 rd reference position, and the N positions are positions of lattice points on an upper surface of the table.

6. The height correction system according to any one of claims 1 to 5,

the inclination of the 1 st ground plane is different from the inclination of the 1 st reference ground plane,

the controller corrects a deviation in height from an upper surface of the table to the front end effector caused by the inclination of the 1 st floor.

7. The altitude correction system according to any one of claims 1 to 6,

the inclination of the 2 nd ground plane is different from the inclination of the 2 nd reference ground plane,

the controller corrects a deviation in height from an upper surface of the table to the front end effector caused by the inclination of the 2 nd floor.

8. The height correction system according to any one of claims 1 to 7,

the work table is different from the work table used for manufacturing the correction table.

9. The height correction system according to any one of claims 1 to 7,

the combination of the carriage and the articulated robot arm is different from the combination of the carriage and the articulated robot arm in making the correction table.